Safe Upper Limits

Among several differences between the three nutritional standards is the presence (or absence) of safe upper limits, or maximum nutrient levels. Here, we’ll examine just a few of these.

FEDIAF, for example, sets maxima for several essential minerals. While calcium and phosphorus carry nutritional maximum levels, trace minerals have legal maximum limits.¹

FEDIAF defines a nutritional maximum as “the maximum level of a nutrient in a complete pet food that, based on scientific data, has not been associated with adverse effects in healthy dogs and cats.” They further advise that levels exceeding the nutritional maximum may be safe, but they currently have no data to verify this possibility.

In contrast, the legal maximum applies to trace minerals and vitamin D coming from nutritional additives. “A legal maximum only applies when the particular trace element or vitamin is added to the recipe as an additive, but relates to the ‘total’ amount present in the finished product (amount coming from the additive plus amount from feed materials (ingredients)). If the nutrient comes exclusively from feed materials, the legal maximum does not apply, instead the nutritional maximum, when included in the relevant tables, should be taken into account.”

In other words, when using supplements to meet copper, zinc, manganese, iron, iodine, selenium, or vitamin D, the total amount cannot exceed the maximum legal level, even if some of that nutrient is coming from food ingredients in the diet. However, if the entire amount of the nutrient is coming from food sources, the legal limit does not apply (but any nutritional limit does).

In contrast, while both AAFCO and NRC have set upper limits for both calcium and phosphorus, neither have such limits on trace minerals.

Recently, AAFCO voted not to establish a copper maximum, as well as voting no to providing a voluntary “controlled copper” label claim option.2 Their Pet Food Committee considered these actions in response to a 2021 article in the Journal of the American Veterinary Medical Association (JAVMA)3, which expressed concern about the increasing incidence of copper-related liver disease in dogs that they postulated may be related to the copper content in American pet
foods.

Both FEDIAF and NRC have set a safe upper limit for the amino acid lysine in canine growth formulations. Both are based on a 1985 study 4 in which puppies fed a diet supplemented with high levels of lysine experienced decreased growth. Neither standard specifies that this limit applies only to excess lysine supplementation, however, it is extremely challenging to formulate a fresh meat-based diet that does not exceed this lysine limit. Therefore, it seems reasonable to wonder if this growth impairment is limited to excess lysine specifically in a supplemental form, versus naturally occurring in animal-based ingredients.

None of the three nutritional standards have set a maximum or safe upper limit for vitamin B9 (folic acid). However, in human nutrition, it is recognized that excess folic acid supplementation is not without risk5, although folate (the form of vitamin B9 found naturally in foods) is safe.

Both supplemental folic acid and folate naturally occurring in foods are represented in the value shown for folic acid in the ADF.